System for simulating power plant of automotive vehicle utilizing electrically powered high inertia power plant

ABSTRACT

A simulation system for an automotive internal combustion engine is suitable for simulating an engine operation for performing a bench test for an engine associated vehicular component, such as an automatic power transmission, an automatic transaxle, a differential gear box, and so forth. The system comprises a power plant which incorporates a relatively high inertia, and means for compensating the high inertia for achieving a low inertia equivalent to the automotive internal combustion engine; an engine characteristics generator receiving predetermined engine operation parameter simulated data for deriving a control signal commanding an output torque of said power plant according to a predetermined engine output torque variation characteristic which is set in terms of said engine operation parameter simulated data, and means, responsive to a simulated engine environmental condition indicative data, for deriving a correction value based on said environmental condition for correcting said control signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to a simulation system for an automotivepower plant, such as an internal combustion engine, for testingautomotive components, such as an automatic power transmission. Morespecifically, the invention relates to an automotive power plantsimulation system utilizing an electrically powered high inertia powerplant, such as an electric motor, which is suitable for bench testingautomotive components, such as an automatic power transmission.

2. Description of the Background Art

Japanese Patent First (unexamined) Publications (Tokkai) Showa 58-38833and 61-53541 disclose bench testing systems for automatic powertransmission. In the disclosed system, an electric motor, a hydrostaticmotor and so forth, are employed as substitute power plants in place ofan automotive internal combustion engine. As can be appreciated, becauseof much higher inertia of the electric motor, hydrostatic motor andother substitute power plants in comparison with the automotive internalcombustion engines, the substitute power plant is combined with speedincreasing devices. Such automotive engine simulation system is usefulfor durability testing, static characteristics testing and so forth.However, due to the substantially high inertia moment, it is practicallydifficult to simulate transition characteristics at transmission speedratio shifting and so forth. For instance, the electric motor hasapproximately 10 times higher inertia magnitude than that of theautomotive engine.

For designing automatic power transmissions with enhanced shift feeling,reduced shift shock and so forth, it is essential to obtain data of thetransition characteristics of power plant to be actually combined withthe test transmission.

Therefore, Tokkai Showa 61-53541 as identified above, employs a strategyof a correction of command current for the electric motor. With thecorrected command current, the output torque of the electric motorbecomes substantially corresponding to the engine output torque to beoutput in response to a torque demand. Such an approach is generallysuccessful in avoiding influence of high inertia of the high inertiapower plant.

In the practical simulation, the automotive engine is simulated in termsof given parameters, such as an engine speed, a throttle valve openangle and so forth. Namely, in order to simulate the automotive enginetransition characteristics for performing a bench test of an automaticpower transmission, an engine speed and a throttle valve open angle areused as parameters for simulation. Therefore, an engine characteristicsgenerator sets torque demand in terms of the engine speed indicativesignal and a throttle valve open angle indicative signal to control thehigh inertia power plant, i.e. electric motor. When shift controlparameters for controlling a shifting transmission gear ratio in theautomatic power transmission is common to those used for simulating theengine characteristics, such approach is successfully introduced forperforming a bench test. However, on the other hand, when the shiftcontrol parameters are different from those utilized for simulating theengine characteristics, difficulty is encountered in performing such abench test. Therefore, it is desirable to provide a simulated enginecharacteristics generator which can perform a bench test of theautomatic power transmissions irrespective of the shifting controlparameters thereof.

On the other hand, in case that the shift control system of theautomatic power transmission employs an intake air pressure as one ofthe shift control parameters, it becomes necessary to provide asimulated intake air pressure indicative data corresponding to thesimulating condition of the engine.

Furthermore, in the modern and advanced automatic transmissiontechnologies, a transmission gear ratio shifting pattern and/or shiftingschedule is set and is variable depending upon various additionalparameters. For instance, sometimes in the shift control system, itbecomes necessary to provide data simulating an environmental condition,such as atmospheric pressure which is variable depending upon altitude.Since the intake air density to be introduced into the automotive engineis variable for causing variation of the engine output characteristics,some of the environmental conditions also affect the engine outputcharacteristics. Therefore, for such type of the automatic powertransmission, it becomes essential to simulate engine characteristicswith the environmental condition indicative parameter or parameters assimulation parameter or parameters.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide asimulation system for simulating an automotive engine characteristicwhich enables a bench test for engine associated vehicular components,such as an automatic power transmission, irrespective of controlparameters set for controlling the vehicular components.

According to one aspect of the invention, a simulation system for anautomotive internal combustion engine, comprises:

a power plant which incorporates a relatively high inertia, and meansfor compensating the high inertia for achieving a low inertia equivalentto the automotive internal combustion engine;

an engine characteristics generator receiving predetermined engineoperation parameter simulated data for deriving a control signalcommanding an output torque of the power plant according to apredetermined engine output torque variation characteristic which is setin terms of the engine operation parameter simulated data; and

means, responsive to a simulated engine environmental conditionindicative data, for deriving a correction value based on theenvironmental condition for correcting the control signal.

The engine output torque variation characteristics may be set in termsof a steady state of the engine at a predetermined standardenvironmental condition. The engine environmental condition indicativedata may be atmospheric pressure, and the correction value is derivedcorresponding to a difference between the atmospheric pressurerepresented by the engine environmental condition indicative data and astandard pressure defining the predetermined standard environmentalcondition. Preferably, the correction value is provided as a correctioncoefficient.

According to another embodiment of the invention, a simulation systemfor an automotive internal combustion engine, comprises:

a power plant which incorporates a relatively high inertia, and meansfor compensating the high inertia for achieving a low inertia equivalentto the automotive internal combustion engine;

an engine characteristics generator receiving predetermined engineoperation parameter simulated data for deriving a control signalcommanding an output torque of the power plant according to apredetermined engine output torque variation characteristic which is setin terms of the engine operation parameter simulated data; and

means for generating associated engine operating parameter data otherthan the predetermined engine operation parameter value.

In the preferred construction, the associated engine operating parameterdata is provided as a physical force magnitude. The associated engineoperating parameter data may be an intake vacuum pressure simulatedcorresponding to the simulated engine operating parameter data. Thepredetermined engine operation parameter simulated data may be enginespeed data and a throttle valve open angle data.

According to a further aspect of the invention, a bench testingapparatus for testing an automotive engine associated vehicularcomponent which is controlled at an operational state depending uponpreselected control parameters, comprising:

a low inertia engine simulating power plant generating a driving torquesimulating engine output, the power plant being cooperated with a samplecomponent to be tested for supplying an engine output simulated drivingtorque;

an engine characteristics generator receiving predetermined engineoperation parameter simulated data for deriving a control signalcommanding an output torque of the power plant according to apredetermined engine output torque variation characteristic which is setin terms of the engine operation parameter simulated data; and means,responsive to a simulated environmental condition indicative datarepresentative of the environmental condition of the sample component,for deriving a correction value based on the environmental condition forcorrecting the control signal.

According to a still further aspect, a bench testing apparatus fortesting an automotive engine associated vehicular component which iscontrolled to an operational state depending upon preselected controlparameters, comprises:

a low inertia engine simulating power plant generating a driving torquesimulating engine output, the power plant being cooperated with a samplecomponent to be tested for supplying an engine output simulated drivingtorque;

an engine characteristics generator receiving predetermined engineoperation parameter simulated data for deriving a control signalcommanding an output torque of the power plant according to apredetermined engine output torque variation characteristics which isset in terms of the engine operation parameter simulated data; and

means for generating at least one of the control parameters forcontrolling the sample component, which one control parameter beingassociated with a simulated engine operating condition.

According to a yet further aspect of the invention, a bench testingapparatus for testing an automotive engine associated vehicularcomponent which is at a controlled operational state depending uponpreselected control parameters, comprises:

a low inertia engine simulating power plant generating a driving torquesimulating engine output, the power plant being cooperated with a samplecomponent to be tested for supplying an engine output simulated drivingtorque;

an engine characteristics generator receiving predetermined first set ofengine operation parameter simulated data for deriving a control signalcommanding an output torque of the power plant according to apredetermined first engine output torque variation characteristic whichis set in terms of the engine operation parameter simulated data, theengine characteristics generator having a second engine output torquevariation characteristics set with respect to a second set of engineoperating parameter simulated data, in which at least one of datarepresentative of different engine operation parameter simulated data isdifferent from that in the first set; and

means for generating at least one of the control parameters forcontrolling the sample component, which one control parameter beingassociated with simulated engine operating condition.

According to a further aspect of the invention, a method for simulatingoperation of an automotive internal combustion engine, comprises thesteps of:

generating an engine output torque simulating driving torque by means ofa power plant which incorporates a relatively high inertia and means forcompensating the high inertia for achieving a low inertia equivalent tothe automotive internal combustion engine;

deriving a control signal commanding an output torque of the power plantin terms of given engine simulating parameters according to apredetermined engine output torque variation characteristic which is setin terms of the engine simulating parameters for simulating engineoperation at a predetermined engine driving condition represented by thegiven engine simulating parameters; and

deriving a correction value based on the environmental condition forcorrecting the control signal.

According to a still further aspect of the invention, a method forsimulating operation of an automotive internal combustion engine,comprises the steps of:

generating an engine output torque simulating driving torque by means ofa power plant which incorporates a relatively high inertia and means forcompensating the high inertia for achieving a low inertia equivalent tothe automotive internal combustion engine;

deriving a control signal commanding an output torque of the power plantin terms of given engine simulating parameters according to apredetermined engine output torque variation characteristic which is setin terms of the engine simulating parameters for simulating engineoperation at a predetermined engine driving condition represented thegiven engine simulating parameters; and

generating associated engine operating parameter data other than thepredetermined engine operation parameter value.

According to a still further aspect, a method for testing an automotiveengine associated vehicular component which is controlled to anoperational state depending upon preselected control parameters,comprises the steps of:

generating a driving torque simulating engine output by means of a lowinertia power plant comprising a relatively high inertia and means forcompensating the high inertia for achieving a low inertia equivalent tothe automotive internal combustion engine,

supplying engine output simulated driving torque to a sample componentto be tested for driving the latter;

deriving a control signal commanding an output torque of the power plantin terms of given engine simulating parameters according to apredetermined engine output torque variation characteristics which isset in terms of the engine simulating parameters for simulating engineoperation at a predetermined engine driving condition represented by thegiven engine simulating parameters;

setting a test condition for the sample component and supplying a testcondition simulating data; and

deriving a correction value based on the environmental conditionrepresented by the testing condition simulating data for correcting thecontrol signal.

According to a yet further aspect, a method for testing an automotiveengine associated vehicular component which is controlled to anoperational state depending upon preselected control parameters,comprises the steps of:

generating a driving torque simulating an engine output by means of alow inertia power plant comprising a relatively high inertia and meansfor compensating the high inertia for achieving a low inertia equivalentto the automotive internal combustion engine,

supplying an engine output simulated driving torque to a samplecomponent to be tested for driving the latter;

deriving a control signal commanding output torque of the power plant interms of given engine simulating parameters according to a predeterminedengine output torque variation characteristic which is set in terms ofthe engine simulating parameters for simulating engine operation at apredetermined engine driving condition represented by the given enginesimulating parameters; and

generating at least one of the control parameters for controlling thesample component, which one control parameter being associated withsimulated engine operating condition.

According to a still further aspect, a method for testing testing anautomotive engine associated vehicular component which is controlled toan operational state depending upon preselected control parameters,comprises the steps of:

generating a driving torque simulating engine output by means of a lowinertia power plant comprising a relatively high inertia and means forcompensating the high inertia for achieving a low inertia equivalent tothe automotive internal combustion engine,

supplying an engine output simulated driving torque to a samplecomponent to be tested for driving the latter;

setting a first engine output torque variation characteristic in termsof a first set of engine operation simulating data;

setting a second engine output torque variation characteristic in termsof a second set of engine operation simulating data including at leastone parameter different from those in the first set;

deriving a control signal commanding an output torque of the power plantin terms of given engine simulating parameters according to the engineoutput torque variation characteristics;

generating at least one of the control parameters for controlling thesample component on the basis of the simulated engine driving conditionand the second engine output torque variation characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of thepreferred embodiment of the invention, which, however, should not betaken to limit the invention to the specific embodiment but are forexplanation and understanding only.

In the drawings:

FIG. 1 is a block diagram of the first embodiment of an automotiveengine simulation system, according to the present invention;

FIG. 2 is a flowchart of a simulation control routine for performingsimulation of the engine characteristics;

FIG. 3 is a chart showing output characteristics of the enginecharacteristics simulation system of FIG. 1;

FIG. 4 is a block diagram of the second embodiment of the automotiveengine characteristics simulation system according to the presentinvention;

FIG. 5 is a chart showing variation of a simulated pressure and intakeair pressure;

FIG. 6 is a block diagram of the third embodiment of the automotiveengine characteristics simulation system according to the presentinvention;

FIGS. 7 and 8 are charts showing different engine characteristics; and

FIGS. 9 and 10 are explanatory charts showing the manner of derivationof an intake air pressure indicative parameter.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, particularly to FIG. 1, there isillustrated a dynamometer for bench testing an automotive automaticpower transmission utilizing the preferred embodiment of an automotiveengine simulation system according to the invention. The shownembodiment of the automatic power transmission employs a low inertiapower plant 1. The low inertia power plant 1 comprises a direct currentmotor which is associated with a thyristor-Leonard type current controlminor loop. The direct current motor may be further associated with aspeed increasing device for compensating high inertia of the directcurrent motor. The motor is controlled by current command or torquecommand generated by the thyristor-Leonard type minor loop. The lowinertia power plant has been disclosed in the co-pending U.S. patentapplication Ser. Nos. 427,031 filed on Oct. 25, 1990, and 436,298 filedon Nov. 13, 1990. The disclosure of the above-identified co-pending U.S.patent application is herein incorporated by reference for the sake ofdisclosure.

The low inertia power plant 1 has an output shaft which is connected toan automatic power transmission 3 to be tested. Therefore, the automaticpower transmission 3 is driven by the output of the low inertia powerplant 1. The output shaft of the automatic power transmission 3 isconnected to a dummy load 5 via a torque meter 4. As the dummy load 5, atorque absorbing dynamometer 5 including a flywheel is utilized.

For controlling the low inertia power plant 1, the automatic powertransmission 3, and the dynamometer 5, respectively separate controlunits 6, 7 and 8 are provided. For the control unit 6, a torque commandor speed command is applied for performing torque or speed control. Thecontrol unit 6 also receives a torque indicative signal T₁representative of the output torque of the low inertia power plant 1from the torque meter 2. Therefore, the control unit 6 performs feedbackcontrol of the low inertia power plant 1 by supplying a torque controlsignal which adjusts the output torque to reduce the difference betweenthe commanded torque indicated in the torque command and the actualoutput torque indicated in the torque indicative signal T₁.

The torque command is generated by the preferred embodiment of an enginecharacteristics generator 9, according to the invention. The enginecharacteristics generator 9 comprises a microprocessor based unit. Theengine characteristics generator 9 is set to provide output torquecharacteristics in relation to a revolution speed N, as shown in FIG. 3.As can be seen from FIG. 3, the output torque characteristics are setrelative to a respective throttle valve open angle θ_(i). Respectiveoutput torque characteristics may also be set through experiments. Theengine characteristics generator 9 processes the throttle valve openangle data θ_(i) and a revolution speed indicative data N which issupplied from a revolution speed sensor 10. On the basis of the throttlevalve open angle data θ_(i) and a revolution speed indicative data N,the torque command value is derived according to the set output torquecharacteristics of FIG. 3.

It should be appreciated that, though the shown embodiment employs thethrottle valve open angle data θ₁ as an engine load indicative data, anintake air vacuum pressure can be utilized.

FIG. 2 shows a flowchart showing operation of the engine characteristicsgenerator 9. For the microprocessor in the engine characteristicsgenerator 9, steady state data θ_(f) which corresponds to the engineoutput characteristics at a constant open angle of the throttle valve ata predetermined standard engine condition is input, at a step S₁. Thesteady state data θ₁ corresponds to the characteristics of θ₀ to θ_(n)in FIG. 3. These steady state data are set on the basis of the engineperformance test data under standard atmospheric pressure. It is alsopossible to set the steady state data θ₁ by arithmetically correctingthe test data in terms of the atmospheric test condition so as to obtainthe data under standard atmospheric condition. Arithmetic correction maybe performed according to the following equation as defined in JISD1001-1982:

    T.sub.0 =K.sub.a ·T.sub.e                         (1)

    K.sub.a ={P.sub.o /(P.sub.a -P.sub.w)}.sup.1.2 ×

    {(273+t.sub.d)/(273+t.sub.0)}.sup.0.8                      (2)

wherein

T₀ is corrected output torque;

K_(a) is correction coefficient S;

T_(e) is standard torque data;

P_(o) is standard dry-bulb pressure;

P_(a) is total atmospheric pressure;

P_(w) is vapor composite pressure in atmosphere;

t_(d) is intake air temperature; and

t_(o) is standard atmospheric temperature (25° C.)

As can be appreciated herefrom, the corrected output torque can beobtained by correcting the standard torque data with the correctioncoefficient.

At a step S₂, environment setting data for defining a testingenvironmental condition is input. Practically, the environment settingdata represents the pressure data P_(o). Based on the input pressuredata P_(o), the correction coefficient K_(a) is derived. Subsequently,at a step S₃, the steady sate data θ_(f) are corrected. Practically,correction for the steady state data is performed by multiplying 1/K_(a)for the steady state data θ_(f)

    θ.sub.c =θ.sub.f ×(1/K.sub.a)            (3)

By the correction set forth above, respective data of the steady statedata θ_(f) set in the step S₁ are modified to be adapted to the settesting condition. Therefore, by inputting desired testing conditiondata (P_(o)), any desired testing condition can be simulated. At a stepS₄, engine output characteristics simulation is performed by supplyingthe torque command to the control unit 6 set forth above. Therefore, inthe shown embodiment, a bench test of the automatic power transmissioncan be performed at any desired test conditions.

For further precision of the bench test of the automatic powertransmission, it is desirable to set the testing condition including atemperature condition. However, since the influence of atmosphericpressure and temperature for performance of the automatic powertransmission is substantially small, it would be sufficient toincorporate the factor of temperature condition in the test condition.Therefore, in the shown process, environmental temperature of theautomatic power transmission is temporarily adjusted to a desiredtesting temperature by means of a cooler, heater or air conditionerunit, at a step S₅. Then, at a step S₆, testing temperature at theenvironment of the automatic power transmission to be tested, is set. Bythis, a further precise bench test for the automatic power transmissioncan be performed.

In case of an automatic power transmission which employs an intakevacuum pressure as one of the shift control parameters, it is essentialto simulate an intake vacuum pressure according to the driving conditionof the low inertia power plant 1. A system for bench testing theautomatic power transmission which requires the intake vacuum pressuredata for shifting control, is illustrated in FIG. 4 in a form ofsimplified block diagram.

As can be seen from FIG. 4, a low inertia power plant 101 has a similarconstruction as discussed with respect to the former embodiment. Namely,the low inertia power plant 101 employs an electric motor as a primemover. The low inertia power plant 101 is controlled by an enginecharacteristics generator 109. For simulating the engine operation, theengine characteristics generator 109 is supplied with an engine speedindicative data N and an intake vacuum pressure indicative data P. Ascan be seen, the engine characteristics generator 109 is set at aplurality of engine output characteristics P₁, P₂ . . . variable inrelation to the engine speed N. The engine characteristics generator 109derives a torque command to control operation of the low inertia powerplant 101.

The low inertia power plant 101 is connected to the automatic powertransmission 103 to be tested for supplying the engine output simulatedoutput torque. The automatic power transmission 103 is connected to adummy load 105 to supply thereto the output torque.

The intake vacuum pressure P is supplied to a converter 110. Theconverter 110 converts the intake vacuum indicative data P into adepression force indicative data. The converter 110 outputs thedepression force indicative data to an adder 111. The adder 111 isconnected to a pressure generator 112 which generates a simulatedpressure corresponding to the intake vacuum pressure at the simulatedengine operating condition. The simulated pressure generated by thepressure generator 112 is monitored by a pressure sensor 113. Thepressure sensor 113 generates a simulated pressure indicative signal tobe fedback to the adder 111. The adder 111 receives the depression forceindicative data at a non-inverting input and the fedback simulatedpressure indicative signal at an inverting input. Therefore, the adder111 supplies a difference signal representative of the differencebetween the depression force indicative data and the simulated pressureindicative signal.

As shown in FIG. 5, the depression force indicative data is set inrelation to the intake vacuum pressure. Namely, as can be seen from FIG.5, the depression force F (kg/cm²) is increased according to adecreasing of the intake vacuum pressure P. The pressure generator 112comprises a pressure generating actuator which is constituted of apressure controller and a master cylinder for generating a fluidpressure, such as a hydraulic pressure, at the magnitude correspondingto the value of the depression force indicative data. The pressure thusgenerated is transferred to the automatic power transmission to betested via a pressure transferring means 114, such as an output shaft ofthe pressure generator 112 for which the generated pressure is exerted.

FIG. 6 shows the third embodiment of the bench testing system includingthe preferred embodiment of the engine characteristics simulationsystem, according to the present invention. The shown embodiment isdesigned to adapted the engine characteristics simulation system tovarious types of automatic power transmissions having mutually differentshift control parameters.

In the shown embodiment, the low inertia power plant 201 receives thetorque command from an engine characteristics generator 209. The enginecharacteristics generator 209 is associated with a plurality of datastorages 209₁, 209₂, 209₃ . . . Respective ones of the data storagestore engine output torque variation characteristics set with respect todifferent parameters. In the shown example, the data storage 209₁ storesthe engine output torque data set in terms of the throttle valve openangle θ and the engine speed N, as shown in FIG. 7. On the other hand,the data storage 209₂ stores the engine output torque data set in termsof the intake vacuum pressure P and the engine speed N, as shown in FIG.8. The engine characteristics generator 209 receives the engine speedindicative data N and the throttle valve open angle data θ. Therefore,basic simulated engine output torque data is derived on the basis of theengine output torque variation characteristics stored in the datastorage 209₁. For example, as seen from FIG. 9, assuming that thethrottle valve open angle is θ_(k) and the engine speed is N₁, thesimulated engine output torque becomes T₁, as seen from FIG. 9. On theother hand, when the simulated engine output torque is T₁ and the enginespeed N is N, the corresponding intake vacuum pressure data P_(k) can bederived from the engine output variation characteristics stored in thedata storage 209₂. Therefore, the engine characteristics generator 209can output the intake air pressure indicative data P in addition to thetorque command T.

In the shown embodiment, the torque command T generated by the enginecharacteristics generator 209 is supplied to the low inertia power plant201 for controlling the output torque of the latter. The enginecharacteristics generator 209 further outputs the intake vacuumindicative data to a pressure generating actuator 210 which may be thesame construction to that in the former embodiment. Therefore, thepressure corresponding to the intake vacuum pressure can be supplied tothe automatic power transmission 203 connected to the dummy load 205.Therefore, in the shown embodiment, a bench test for the automatic powertransmission 203 is enabled even when the parameters used for shiftcontrol are different from those input to the engine characteristicsgenerator 209.

As can be clear from the above, the present invention successfullysimulates the automotive internal combustion engine. Also, the presentinvention enables bench testing for the automatic power transmissionseven when the parameters to be used for controlling shifting of thetransmission gear ratio are different from that supplied to the enginecharacteristics generator.

While the present invention has been discussed in terms of the preferredembodiments of the invention, the invention may be embodied in variousways. Therefore, the invention should be interpreted to include allpossible embodiments and modifications which can be implemented withoutdeparting from the principle of the invention.

What is claimed is:
 1. A simulation system for an automotive internalcombustion engine applicable to a testing of a vehicular powertransmission, comprising:a power plant which incorporates a relativelyhigh revolution inertia and having means for compensating said highinertia for achieving a low inertia substantially equivalent to theautomotive internal combustion engine; an engine characteristicsgenerator for receiving predetermined engine operation parametersimulated data and for deriving a control signal for commanding anoutput torque of said power plant according to a predetermined engineoutput torque variation characteristic which is set in terms of saidengine operation parameter simulated data; and means responsive to asimulated engine environmental condition indicative data for deriving acorrection value based on an environmental condition for correcting saidcontrol signal.
 2. A simulation system as set forth in claim 1, whereinsaid engine output torque variation characteristic is set in terms of asteady state of the engine at a predetermined standard environmentalcondition.
 3. A simulation system as set forth in claim 2, wherein saidengine environmental condition is atmospheric pressure, and saidcorrection value is derived corresponding to a difference between anatmospheric pressure represented by said engine environmental conditionindicative data and a standard pressure defining said predeterminedstandard environmental condition.
 4. A simulation system as set forth inclaim 3, wherein said correction value is provided as a correctioncoefficient.
 5. A simulation system for an automotive internalcombustion engine applicable to a testing of a vehicular powertransmission, comprising:a power plant which incorporates a relativelyhigh inertia and means for compensating said high inertia for achievinga low inertia equivalent to the automotive internal combustion engine;an engine characteristics generator for receiving predetermined engineoperation parameter simulated data and for deriving a control signal forcommanding an output torque of said power plant according to apredetermined engine output torque variation characteristic which is setin terms of said engine operation parameter simulated data; and meansfor generating associated engine operating parameter data in addition tosaid predetermined engine operation parameter simulated data.
 6. Asimulation system as set forth in claim 5, wherein said associatedengine operating parameter simulated data is provided as a physicalforce magnitude.
 7. A simulation system as set forth in claim 6, whereinsaid associated engine operating parameter simulated data is an intakevacuum pressure simulated corresponding to the engine operatingparameter simulated data.
 8. A simulation system as set forth in claim7, wherein said predetermined engine operation parameter simulated dataare an engine speed data and a throttle valve open angle data.
 9. Amethod for simulating operation of an automotive internal combustionengine, comprising the steps of:generating an engine output torquesimulating driving torque by means of a power plant which incorporates arelatively high inertia and means for compensating said high inertia forachieving a low inertia equivalent to the automotive internal combustionengine; deriving a control signal for commanding an output torque ofsaid power plant in terms of given engine simulating parametersaccording to a predetermined engine output torque variationcharacteristic which is set in terms of said engine simulatingparameters for simulating engine operation at a predetermined enginedriving condition represented by said given engine simulatingparameters; and deriving a correction value based on an environmentalcondition for correcting said control signal.
 10. A method for testingan automotive engine associated vehicular component which has acontrolled operational state depending upon preselected controlparameters, comprising the steps of:generating a simulated enginedriving torque output by means of a low inertia power plant comprising arelatively high inertia and means for compensating said high inertia forachieving said low inertia which is equivalent to the automotiveinternal combustion engine; supplying said simulated engine drivingtorque output to said associated vehicular component to be tested fordriving the latter; deriving a control signal for commanding saiddriving torque of said power plant in terms of given engine simulatingparameters according to a predetermined engine output torque variationcharacteristic which is set in terms of said engine simulatingparameters for simulating engine operation at a predetermined enginedriving condition represented by said given engine simulatingparameters; setting a test condition for said associated vehicularcomponent and supplying a test condition simulating data; and deriving acorrection value based on an environmental condition represented by saidtest condition simulating data for correcting said control signal.
 11. Amethod for simulating operation of an automotive internal combustionengine, comprising the steps of:generating an engine output torquesimulating driving torque by means of a power plant which incorporates arelatively high inertia and means for compensating said high inertia forachieving a low inertia equivalent to the automotive internal combustionengine; deriving a control signal for commanding an output torque ofsaid power plant in terms of given engine simulating parametersaccording to a predetermined engine output torque variationcharacteristic which is set in terms of said engine simulatingparameters for simulating engine operation at a predetermined enginedriving condition represented by said given engine simulatingparameters; and generating associated engine operating parameter data inaddition to said predetermined engine operation parameter value.
 12. Abench testing apparatus for testing an automotive engine associatedvehicular component which has a controlled operational state dependingupon preselected control parameters, comprising:a low inertia enginesimulating power plant generating a driving torque simulating engineoutput, said power plant being cooperated with said associated vehicularcomponent to be tested for supplying said driving torque; an enginecharacteristics generator for receiving predetermined engine operationparameter simulated data and for deriving a control signal forcommanding an output torque of said power plant according to apredetermined engine output torque variation characteristic which is setin terms of said engine operation parameter simulated data; and meansresponsive to a simulated environmental condition indicative datarepresentative of an environmental condition of said associatedvehicular component for deriving a correction value based on saidenvironmental condition for correcting said control signal.
 13. A benchtesting apparatus as set forth in claim 12, wherein said engine outputtorque variation characteristics is set in terms of a steady state ofthe engine at a predetermined standard environmental condition.
 14. Abench testing apparatus as set forth in claim 13, wherein saidenvironmental condition is atmospheric pressure, and said correctionvalue is derived corresponding to a difference between an atmosphericpressure represented by said simulated environmental conditionindicative data and a standard pressure defining said predeterminedstandard environmental condition.
 15. A simulation system as set forthin claim 14, wherein said correction value is provided as a correctioncoefficient.